Scott Pruitt, Chief of the US Environmental Protection Agency (EPA), has reversed the decision to delay implementing emissions reduction rules.
The laws, which were set in motion during the Obama Administration, aim to reduce the amount of ground-level ozone – this is created when emissions from cars, power plants and other sources react with sunlight to create harmful smog.
In June, Mr Pruitt announced he would delay compliance by one year to give the agency more time to study the plan and avoid “interfering with local decisions or impeding economic growth”.
The former Oklahoma State Attorney was then sued by 15 states, triggering his change of decision.
He said: “The EPA’s reversal following our lawsuits is an important win for the health and safety of those 6.7 million New Yorkers and the over 115 million Americans directly impacted by smog pouring into their communities.”
Many prominent Republicans are pushing for a deeper rewrite of the ground-ozone rules – a bill approved last month seeks to delay their implementation by at least eight years.
The Trump Administration has moved to block or delay regulations opposed by the chemical and fossil-fuel industries a number of times in the past, as well as leaving the Paris Agreement on climate change.